U.S. patent number 4,466,553 [Application Number 06/299,982] was granted by the patent office on 1984-08-21 for composite container construction.
This patent grant is currently assigned to National Can Corporation. Invention is credited to Richard D. Zenger.
United States Patent |
4,466,553 |
Zenger |
August 21, 1984 |
Composite container construction
Abstract
A container for vacuum packaging of products includes an outer
container and an inner liner which conforms generally to the
configuration of the outer container and is secured to the upper
open end thereof while the remainder of the container and liner are
unattached. A vent is provided between the atmosphere and the space
between the container and liner so that the liner can expand and
collapse as differential pressures are applied to the product
sealed in the liner by a plastic film secured open end thereof.
Inventors: |
Zenger; Richard D. (Downers
Grove, IL) |
Assignee: |
National Can Corporation
(Chicago, IL)
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Family
ID: |
26842094 |
Appl.
No.: |
06/299,982 |
Filed: |
September 8, 1981 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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144545 |
Apr 28, 1980 |
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Current U.S.
Class: |
220/495.08;
206/524.8; 206/583; 220/258.2; 220/288; 220/609; 220/666; 220/672;
229/117.29 |
Current CPC
Class: |
B65D
25/18 (20130101) |
Current International
Class: |
B65D
25/18 (20060101); B65D 25/14 (20060101); B65D
025/18 (); B65D 051/20 () |
Field of
Search: |
;220/403,404,461,460,258,469,426 ;229/43
;426/115,124,398,399,404,116,125,401,411,412 ;53/432,434 ;215/232
;222/95 ;206/583,524.8 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2289123 |
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May 1976 |
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FR |
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350598 |
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Jan 1961 |
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CH |
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430256 |
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Jun 1935 |
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GB |
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1161363 |
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Aug 1969 |
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GB |
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Other References
"Nature Fresh in Latex", Modern Packaging, Aug. 1941, pp. 44,
45..
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Primary Examiner: Shoap; Allan N.
Attorney, Agent or Firm: Stenzel; Robert A. Rath; Ralph
R.
Parent Case Text
This application is a divisional application of U.S. Ser. No.
144,545, filed Apr. 28, 1980, now abandoned.
Claims
I claim:
1. A container for packaging a product comprising: an outer
container having a bottom wall and a sidewall with an open top and
a rim around said open top; a collapsible inner liner loosely
positioned within said outer container and forming a space
therebetween, said inner liner having an open end substantially
aligned with said open end of said outer container to permit
filling of said liner with said product during which said liner
conforms to said outer container; a rigid ring around the open end
of the inner liner and defining a downwardly-opening channel
receiving said rim with said liner supported by said rigid ring to
secure said liner to said outer container while allowing said liner
to flex to change the volumetric capacity of said inner liner; said
rigid ring having a locking rib engaging an inner lower portion of
said rim and a locking ledge engaging a lower outer portion of said
rim to provide a lock for said ring to said rim and seal adjacent
said open end of said space between said liner and said container,
a cover liner sealed to said rigid ring for sealing said open end
of said inner liner after insertion of said product, said rigid
ring having an annular recess for receiving a peripheral portion of
said cover liner, an overcap releasably secured to said rigid ring
and having a peripheral portion engaging said cover liner in said
annular recess to clamp said cover liner to said rigid ring, means
for venting said space between said outer container and inner liner
as said inner liner contracts due to a vacuum therein, thereby
preventing the formation of a vacuum in said outer container, and
means for hermetically sealing said means for venting after said
product has been processed.
2. A container as defined in claim 1, in which said means for
venting includes an opening in said outer container leading to the
space between said container and said liner.
3. A container as defined in claim 1, in which said outer container
is a metal container.
Description
TECHNICAL FIELD
The present invention relates generally to composite container
constructions and more particularly, to a composite container that
is specifically designed to be hermatically sealed for containing
vacuum packaged products.
BACKGROUND PRIOR ART
Proposals for composite containers have been in existance for a
number of years. Generally, the composite container consists of an
outer container that has some type of strength characteristics and
an inner liner which is normally of a flexible plastic material
that can be hermatically sealed. An example of an earlier version
of a composite container is shown in U.S. Pat. No. 2,338,604.
Other examples of composite container constructions are disclosed
in the following U.S. Pat. Nos.:
2,082,995; 3,285,461; 3,383,026; 3,620,399; 3,790,021; 4,141,466;
and 4,169,540.
For many years, attempts have been made to substitute some type of
package for the conventional metal container that is utilized for
packaging of food products, such as vegetables and coffee. In the
packaging or canning of vegetable products, it has been customary
to provide a rigid metal container that is corrugated around the
cylindrical peripheral intermediate portion to provide rigidity for
the container and allow it to withstand crush pressures as well as
resist collapsing during various phases of packaging and processing
of the product therein. Conventionally, in the packaging of
sanitary food products, the metal container must be internally
lined to prevent any contamination of the product during processing
and storage prior to ultimate use.
In the processing of food products, such as vegetables, it is
standard practice to place raw vegetables into the open end of the
container, supply a negative pressure to the product to remove all
oxygen from the inside of a container and seal an end to the open
ended container while the vacuum is being applied to the internal
area of the container. After the container has been sealed, the
container with the product therein is normally passed through some
type of heating process wherein the product is heated for a short
period of time in the range of at least 250.degree. F. During such
heating, the product of course expands and the container has
internal pressures applied thereto. However, upon cooling, after
the finishing of the process, the food product again contracts and
therefore the inside of the container again is at a negative
pressure which the container must withstand without collapsing.
In packaging other products, such as coffee, the product is placed
in a container, a vacuum is applied thereto and the container is
sealed resulting in a vacuum inside the container which the
container withstands without collapsing. Some other products are
hot filled, sealed and then cooled which also results in a negative
pressure in the container.
In the transportation of various articles, many times the articles
are stacked in numerous cases upon each other which means that the
lower container must be capable of resisting substantial crush
pressure from the remaining containers supported thereon. It is
also possible for the containers to be dropped and again the
container must withstand the forces encountered without
collapsing.
Numerous attempts have been made to substitute various types of
less expensive and less rigid packages particularly for food
products and an example that has been dealt with for a number of
years is what is commonly referred to as a "retort" pouch. In order
to meet the various governmental requirements, the typical pouch
construction consists of a layer of polypropylene attached through
an adhesive to an aluminum foil layer with a further polyester
layer adhesively secured to the opposite surface of the foil. The
aluminum foil provides the oxygen barrier resistance that is
required for packaging such products while the polypropylene is
utilized to provide chemical inertness for the product and the
polyester layer produces the necessary mechanical strength for the
pouch.
One of the main problems with a pouch of this type, when used for
packaging food products, is the fact that the relatively flexible
package slows the filling speeds of the filling line and therefore,
increases the cost thereof. For example, pouches of this type
require a special system that will provide a mechanical support for
the pouch during the heating or processing operation for the
contents.
A further problem that has been encountered with the pouch type
package is the fact that the pouch does not have sufficient
rigidity to be self-supporting without collapsing during shipment
and display. Thus, most pouches that are utilized for packaging,
particularly food products, are, of necessity, placed in an outer
cardboard or other carton for shipment and display purposes, adding
to the overall cost of the package.
SUMMARY OF THE INVENTION
According to the present invention, a container has been developed
which has less structural requirements than a conventional metal
can without sacrificing filling speeds such as occur when using
flexible containers.
The container of the present invention comprises a composite
container construction including an outer container that has a
bottom wall and rigid side wall with an open top and an inner
non-metallic container or liner having a closed bottom wall and a
side wall which corresponds substantially in configuration to the
outer container and has an open top for receiving a product. The
inner and outer containers are attached to each other along the
upper open peripheral end and are separated throughout the
remaining area. The outer container provides structural rigidity to
meet stacking and abuse resistance requirements.
The space between the two containers is initially vented to the
atmosphere through an opening in the outer container so that the
inner container can expand and contract in response to positive and
negative pressures applied to the inner surface of the container
from a product during filling and processing of the product.
The composite container also includes a cover for sealing the open
end of the inner container or liner after insertion of the
product.
With the container construction described above, the inner
container is adapted to receive the product during a normal filling
process and normally has a negative pressure or vacuum applied
thereto after the product has been inserted therein to remove all
of the "head space" oxygen before the container is sealed. Also,
the product is many times processed after it has been inserted into
the container and a vacuum seal has been applied. The container
construction of the present invention allows the inner liner to
expand and contract during heating and cooling of the product while
the outer container remains substantially at atmospheric pressure
both on the inside surface and the outside surface thereof to
reduce the forces that must be encountered by the outer container
and the outer container is later sealed.
In one embodiment of the present invention, the inner and outer
containers are both formed in a thermoforming operation and the
inner container has a rigid peripheral ring surrounding the open
end thereof while the outer container has a peripheral rim along
the upper open end thereof. The rim and ring are constructed such
that the ring can be snapped onto the outer container and
releasably retained thereon. In addition, the cover preferably
includes a heat sealable plastic film that is heat sealed to a
surface of the ring prior to insertion of an overcap over the ring
which is releasably retained thereon and can be utilized as a cover
after the film has been removed for gaining access to the contents.
In this embodiment of the invention, the periphery of the film is
heat sealed to a flat surface that is defined in a recess extending
from the upper surface of the ring so that the surface is displaced
below the major upper surface of the ring. In this embodiment, the
overcap portion of the cover is specifically configured so that the
periphery of the film is clamped between the cover and the surface
on the ring to assist in preventing the destruction of the seal
during processing of the product.
In another form of the invention, the ring has peripheral threads
formed integral with the outer surface of the ring and the overcap
has cooperating threads so that the overcap can be threadedly
secured and easily removed. In this embodiment of the invention,
the plastic film may be used if desired. However, in some processes
it may not be necessary to provide a separate sealing film in
addition to the overcap.
In a further modified form of the invention, the ring has a sealing
surface that is located on the periphery thereof and extends
axially of the inner container with the cover film heat sealed to
this surface to aid in resisting forces that may be encountered
during packaging and processing of the product. The cover engages
and grips the sealed area of the film to assist in resisting shear
forces that are encountered by the seal while locating the seal in
such a manner that it cannot be contaminated by the filling
operation which could result in an ineffective seal.
In a further modified form of the invention, the outer container is
a conventional three piece metal container that has an end doubled
seamed to one end thereof. The opposite open end is adapted to
receive the inner container or liner which can be temporarily
secured to an outwardly directed flange thereon for temporarily
holding the liner during the filling process. After the product has
been inserted into the inner liner, the upper edge of the liner and
the periphery of an end or closure are doubled seamed to the upper
end of the outer container so that the inner liner remains
completely unattached from the outer container except around the
upper peripheral edge thereof. The space between the inner and
outer containers is again vented so that the inner liner can expand
and contract to response to variation in pressure within the inner
container while the outer container defines a rigid structure which
provides a second impermeable barrier upon the later sealing of the
vent.
Utilizing the concept of the present invention as a substitute for
the conventional corrugated metal can, particularly the three piece
metal can, has many advantages. For example, the composite
container allows for reduction in the structural requirements for
the outer container and the end and wall thickness can be reduced
by as much as 50% while the lead contamination problem is
eliminated because the product does not come in contact with the
lead seam.
In a further modified form of the invention, the composite
container includes a further or third intermediate liner between
the inner and outer container components and the various liners may
be formed from different materials having different
characteristics. In this embodiment of the invention, the cover can
either be snap fitted onto the upper end of the container or
alternatively may be hingedly secured along one edge. Preferably,
the inner container is filled prior to attaching the cover by a
heat sealable plastic film, which could also be connected through a
hot melt or other types of adhesives, depending upon the chemical
composition of the film as well as the surface to which it must be
sealed.
BRIEF DESCRIPTION OF SEVERAL VIEWS OF DRAWINGS
FIG. 1 is an exploded perspective view, partially in section,
showing a container constructed in accordance with the present
invention;
FIG. 2 is an enlarged fragmentary sectional view, as viewed along
line 2--2 of FIG. 1, showing container in its final sealed
condition;
FIG. 3 is a view similar to FIG. 2 showing a slightly modified form
of the invention;
FIG. 4 is a view similar to FIG. 1 showing a further modified form
of the invention;
FIG. 5 is a cross-sectional view, as viewed along line 5--5 of FIG.
4;
FIG. 6 is a cross-sectional view of a further modified form of
container construction;
FIG. 7 is an exploded perspective view of a still further modified
form of the invention;
FIG. 8 is a fragmentary cross-sectional view of the container
illustrated in FIG. 7 and shown in the closed and hermatically
sealed condition.
DETAILED DESCRIPTION
While this invention is susceptible of embodiment in many different
forms, there is shown in the drawing and will herein be described
in detail preferred embodiments of the invention with the
understanding that the present disclosure is to be considered as an
exemplification of the principles of the invention and is not
intended to limit the invention to the embodiments illustrated.
FIG. 1 of the drawings discloses a container, generally designated
by reference numeral 10, having a cover generally designated by
reference numeral 12. Container 10 consists of an outer shell 14
which may be of a variety of materials and has been illustrated as
being a thermoformed plastic container that has an integral side
wall 16 and a unitary end wall 18 on one end thereof with an
opposite open end. The outer container 14 is preferably formed from
a material that is oxygen impermeable and has a rim 19 formed
around the open end by reverse bending the upper edge of side wall
16. The outer container may also be light impermeable.
An inner container 20 consists of substantially cylindrical side
wall 22 having an integral end wall 24 both of which conform
generally to the configuration of the outer container 14. The inner
container has a rigid ring 26 at the upper open end thereof and the
ring defines a substantially U-shaped downwardly directed channel
28. The side wall of the inner container 20 also has a corrugated
portion 30 and is attached to the outer container by having the
ring 26 snapped over the peripheral rim 19 around the upper opened
end of the container shell 14. Thus, the entire inner container is
free from the outer container 14 except along the upper peripheral
edge thereof and conforms to the outer container while the
corrugated portion allows the inner container to collapse due
internaal negative pressure resulting under certain conditions, as
will be explained later. A collapse or flexing inward is desired
since under Boyles law as the volume is decreased the pressure will
increase and the differential pressure to which the inner container
is subjected to will be less. This allows the use of thinner walled
inner containers.
As illustrated in FIG. 2, the inner or the upper peripheral rim 19
of outer container 14 is substantially U-shaped in cross-section
and defines a downwardly directed lip or ledge 32 around the upper
perimeter of outer container 14. Likewise, the substantially
U-shaped ring 26 has an inwardly directed lip or ledge 34 that
engages ledge 32 to securely hold the inner container shell 20 onto
the outer container shell 14. If desired the molded inner container
shell 20 may also have an outwardly directed rib 36 that engages
the lower inner surface of rim 19 to securely lock the inner
container 20 with respect to the outer container 14.
The inner container or shell 20 is also preferably formed from a
thermo plastic material which may be thermoformed on a mass
production basis. It is preferred that a solid state pressure
thermoforming process be used so fabrication can take place just
prior to the material reaching the plastic state so that a
biaxially oriented product is produced. A process of this type is
disclosed in U.S. Pat. No. 4,172,875.
The cover 12 consists of an inner liner 40 which preferably has its
peripheral edge heat sealed to an upper surface of plastic ring 26.
As illustrated in FIG. 2, the upper inner peripheral surface of
ring 26 has a recessed portion to define a substantially flat
peripheral ledge 42 surrounding the upper open end of inner
container shell 20. The liner or heat sealable plastic film 40 is
preferably heat sealed to ledge 42 to hermatically seal the inner
container 20 from the atmosphere. The cover also includes an
overcap or member 44 which is again attached to the upper
peripheral open end of container 10. For this purpose, the overcap
or cover 44 has a downwardly directed flange 46 around the
periphery thereof, the lower end of which has an inwardly directed
rib 48. Rib 48 is adapted to be snapped over the outer periphery of
ring 26 and engage a lower edge 50 on the lower periphery thereof
to releasably retain the overcap on the container. The overcap
protects the film from damage and permits stacking without
subjecting the film to stacking forces.
According to one aspect of the present invention, the overcap 44 is
designed to assist in maintaining the hermatic seal between the
plastic film 40 and the inner container 20. As illustrated in FIG.
2, the central portion 52 of the overcap 44 is displaced downwardly
from the upper peripheral surface of overcap 44 by a dimension that
is substantially equal to the depth of the recess defining ledge
42, less the thickness of film 40. The periphery of recessed
circular flat portion 52 overlaps with ledge 42 so that, when the
overcap is in the position illustrated in FIG. 2, the peripheral
edge of recessed or dished portion 52 engages the periphery of film
40 and clamps the film between the ledge 42 and the inner surface
of center portion 52. This feature substantially increases the
forces that can be encountered by the heat seal between the film 40
and the adjacent surface of ledge 42 since the film is essentially
gripped between the overcap 44 and the ring 26. By locating the
heat seal in the area clamped between the overcap and the ring, the
seal is maintained in a shear mode and thus the requirements for
the seal are reduced and the bond can maintain substantial
pressures, particularly negative pressures. However, when it is
desired to remove the heat sealed film, it is only necessary to
remove the overcap 44 and grip a tab T forming part of the film 40
to remove the film. The seal between the film and the ring can thus
be high in shear strength and weak in peel strength to permit easy
removal of the entire film from the container to gain access to the
contents.
The container described above normally is initially assembled by
having the inner container 20 positioned within the outer container
14 and attached by the rim. The product is then inserted into the
inner container and the film 40 is heat sealed to ledge 42 while a
vacuum is being applied to the interior of the container to provide
a vacuum packing of the material.
In other instances, a hot product is inserted into the container
and sealed and a negative pressure is created as the product cools.
In heat treatment of the product, a cold product may be inserted
and the container vacuum sealed. The sealed container and product
are then heated which causes the product and the inner container to
expand and then contract when the product is cooled.
As indicated above, one of the problems encountered with containers
of this type is to have the ability of the container to withstand
positive and negative pressures during the processing of the
product within the container.
According to the present primary aspect of the present invention,
the composite container constructed in accordance with the present
invention has vent means between the inner and outer containers to
vent the space between the two containers during filling and
processing of the container. As illustrated in FIG. 1, the bottom
wall 18 of outer container 14 has a vent opening 60 therein which
provides communication from the space between the two container
shells to the atmosphere. Thus, during the application of negative
pressures within the inner container, the container can collapse,
with the collapsing being controlled or restricted to the
corrugated area 30 of the inner container. During this contraction
of the inner container, while vacuum is being applied therein, the
space between the inner and outer container is maintained at an
atmospheric pressure so that the outer container need not be
subjected to the negative pressures that are being subjected to the
inner container. This particular feature is of significant
advantage in reducing the structural rigidity requirements for the
outer container to prevent collapsing thereof while negative
pressures are being applied to the product.
Furthermore, during the filling process, the outer container
provides sufficient rigidity so that filling speeds are not
impaired as is the case with flexible containers or pouches. During
the filling at rapid filling speeds, the inner container wholly
conforms to and is supported by rigid outer container.
Thus, the container of the present invention can readily have the
product inserted therein, vacuum applied to the interior of the
inner container to remove all of the oxygen therefrom and then have
the inner lid of film 40 heat sealed to the upper edge thereof.
With the product within the container, if the product is a raw
vegetable, the sealed container can be utilized for processing of
the product by applying heat thereto or submersing the product
within the container in heated water. During such time, the
expansion of the product as it is being heated will be absorbed by
the inner container without subjecting the outer container to any
significant pressures since the space between the inner and outer
container is still maintained at atmospheric pressure through the
vent opening 60.
Of course, after the product has been processed and is cooled, the
inner container will again be subjected to a negative pressure
which will cause the container to collapse in a controlled manner
while the space between the two containers is still maintained at
atmospheric pressure. When the product has been fully processed and
returns to room temperature, the vent opening can be sealed by a
suitable sealing element 62 such as a foil tab, a hot melt, or any
other suitable seal that is impervious to oxygen so that the outer
container will act as an oxygen barrier between the atmosphere and
the product. If desired, the seal, such as tab 62 could be utilized
for insertion or injection of a controlled or inert gas between the
inner and outer structures prior to being sealed off and providing
an oxygen barrier. This may be particularly beneficial in
strengthening the outer container against abuse resistance while
improving column load strength with ultra-thin side wall thickness.
Another variation would be to insert an absorbent material between
the liner and outer container that could absorb gases that might
permeate the liner. In the case of coffee packaging, vacuum packed
coffee may generate carbon dioxide gas during storage and display.
This carbon dioxide could be absorbed by the absorbent material
should it migrate through the inner container.
If the product is a vegetable and the outer container is metal,
such as a drawn metal container, the inner container can be removed
and placed into a microwave oven, since the inner container
contains no metal.
An additional feature is that the cover 44 can be used to reclose
the inner container for storage of the product if it is not all
consumed when film 40 is removed and film 40 may be translucent to
permit viewing of the product.
A slightly modified form of the invention is illustrated in FIG. 3
which is similar to FIG. 2. In the modified form of the invention,
the outer container 14 is substantially identical to the container
illustrated in FIGS. 1 and 2 while the inner container is modified
as will now be described. In this embodiment of the invention, the
inner container consists of a substantially rigid ring 26a that is
preferably formed from a plastic material that has heat sealing
characteristics and again has a recess 70 defining a ledge 72. In
this embodiment of the invention, the inner container consists of a
flexible bag or pouch 74 that has its upper peripheral edge heat
sealed to the inner surface of ring 26a. Pouch 74 is preferably
formed from a plastic polyolefin film such as polypropylene and two
sheets of such film are heat sealed along their edges and bottom so
that they can be separated to conform generally to the shape of the
outer container. In this embodiment of the invention, the upper
ring 26a has threads 75 formed on the outer peripheral surface
thereof while the overcap 44a has cooperating threads 76 formed on
the internal peripheral surface thereof. The cover in the
embodiment illustrated in FIG. 3 again includes a heat sealable
film 78 that is heat sealed to ledge 72 in the same manner as that
disclosed in the embodiment of FIGS. 1 and 2. In addition, the
overcap 44a again has a dish portion 52a that has its periphery in
engagement with the heat sealing connection between film 78 and
ledge 72.
As in the previous embodiment, the outer container 14 has a vent
opening 60 so that the flexible pouch 74 can expand and collapse
when positive and negative pressures are applied to the interior of
the pouch during the filling and processing of the product
therein.
A slightly further modified form of the invention is illustrated in
FIGS. 4 and 5 and again consists of an outer container 14b that is
substantially identical to container 14 with the exception of the
upper rim 19b which is in the form of a curl, as more clearly
illustrated in FIG. 5. In the embodiment illustrated in FIGS. 4 and
5, the inner container 20b has a corrugated lower wall 80 which is
collapseable and expansible to accommodate negative and positive
pressures within the inner container and performs the same function
as corrugations 30 in the embodiment illustrated in FIG. 1. In this
embodiment, the inner container 20b is preferably thermoformed from
a heat sealable plastic material while the outer container 14b
again has a vent opening 60b in the lower wall thereof which is
closeable by a plug 62b after the contents have been inserted into
the inner container and sealed and processed.
According to one aspect of this embodiment of this invention, the
heat sealing of the cover film to the inner container occurs at a
location which will again assist in preventing destruction of the
seal when positive or negative pressures are applied within the
sealed container. As illustrated in FIG. 5, the ring 26b has a
peripheral surface 82 which extends substantially parallel to the
axis of the circular container and has an enlarged portion 84
located above surface 82. The cover film 86 extends across the
upper surface of the rim or ring 26b, downwardly over the enlarged
portion 84 and in juxtaposed relation to surface 82 wherein it is
heat sealed to the surface. During the heat sealing, the film will
conform to provide a tight seal along enlarged portion 84 and a
hermatic seal along surface 82.
In this embodiment of the invention, overcap or cover 88 has an
upper flat wall 89 which engages the upper flat surface of film 86
and a peripheral depending flange 90 having an enlarged portion 100
at the lower end thereof. The enlarged lower end portion 100
defines a ledge 102 that cooperates with a corresponding ledge 104
on ring 26b.
Thus, in its fully assembled condition as illustrated in FIG. 5,
the heat sealed area between film 86 and rim 26b which also could
be a hot melt or other bonding agent, extends axially of the
container outside ring 26b and the overcap 88 is in extended
engagement with the sealed area between the film 86 and the rim
26b. It will also be appreciated that since the sealing area is
located outside the filling area on the outer surface of the ring,
contamination of the seal from the product during the filling
operation is substantially eliminated.
In its sealed condition, the seal will have a high shear strength
and a weak peel strength since the peeling of the film will result
in forces perpendicular to the sealing surface rather than
tangentially thereto. Again, a suitable tab 106 may be attached to
the periphery of the film for removal when the contents are to be
removed.
It should also be noted that in all of the embodiments so far
described, the upper end of the outer container is necked in to
reduce the material requirements for the cover and could be necked
in sufficiently so the periphery of the reclosable cover would be
within the confines of the periphery of the side wall of the outer
container to simplify handling and processing of the filled
containers.
A further slightly modified form of the invention is illustrated in
FIG. 6, wherein a conventional 3-piece metal can 110 is utilized as
the outer container and includes a cylindrical body 112 having an
end 114 double seamed by a seam 116 to the lower end thereof. The
end 114 has the vent opening 118 which is closed by a plug or other
member 120, as will be described later. The inner container 122 is
preferably a flexible polyolefin plastic such as polypropylene,
which is formed as a flexible bag or pouch. In this embodiment of
the invention, the upper peripheral edge of the outer container
initially has an outwardly directed flange (not shown) extending
substantially perpendicular to the axis of the cylindrical body 112
which is subsequently utilized in attaching an uppr end 124 by a
double seaming 126. Preferably, the inner flexible bag or container
122 is initially bonded to the outwardly directed flange prior to
insertion to the product therein and conforms generally to the
configuration of the outer container. A product may then be
inserted into the inner bag 122, vacuum applied thereto and upper
end 124 doubled seamed thereto as illustrated at 126 with the
double seam also incorporating the upper peripheral edge of bag 122
to provide a seal between the upper edge of the outer container 110
and the upper edge of the bag 122. Vent opening 118 is unobstructed
during the filling and seaming process so that the space between
the inner and outer containers is vented to the atmosphere to allow
the bag to expand and contract during filling and processing while
the outer container is exposed to atmospheric pressure on both the
inner and outer surfaces. After the container has been filled and
the contents fully processed, the plug 120 is inserted into vent
opening to provide a substantially oxygen impervious outer
container which need not be of sufficient rigidity to be subjected
to the negative forces encountered by the inner flexible bag.
In fact, it has been determined that, when the container 110 is
used for vacuum packaging of products, such as coffee and
vegetables, the conventional corrugations on present day containers
can be eliminated and the wall thickness of cylindrical body 112
can be substantially reduced to reduce the cost of the container.
Furthermore, lead contamination, which has become a severe problem
recently, is eliminated because the product is not exposed to the
surface of the metal container. Thus, the coating requirements for
the inner surface can be reduced and in some instances
eliminated.
The outer container side wall seam 113 may be produced by several
methods such as soldering, welding, or gluing. Its preferential use
would be tinless steel for the outer container so as to reduce cost
as tin, which is a component of solder, is becoming a scarce
element. Such tinless steel is referred to as black plate or tin
free steel, which is steel with a chrome oxide coating to provide
corrosion resistance comparable to tinplate. As the product does
not contact the outer container it is thus possible to use black
plate or tin free steel that may have the sidewall adhesively
bonded with hermetic materials that could not normally be used for
contact with foods but provide excellent adhesion and hermetic
sealing qualities. Such a construction also permits fully
lithographed containers that improve the display area by not having
a void margin as is the case with a soldered or welded container.
The problems of iron pickup by corrosive products packaged in
three-piece side wall joined is eliminated as is the absorption of
lead into the food in the case of a soldered container by providing
a barrier between the product and the outer container with the
inner liner. It may be further possible to eliminate or gently
reduce the sealing gasket material within the ends that creates a
hermetic seal at the double seam 116 or 126 in a standard can. Many
food cans require protective coatings that may not be required due
to the lack of product contact mentioned which would result in
reduced process operations including incineration of the solvents
to reduce air pollution that are required to apply the protective
coatings.
By way of example and not of limitation, a present day conventional
three pound coffee can is made from a 107 pound (0.1177inch wall
thickness) tin plate coated steel having corrugations intermediate
opposite ends. Utilizing the present invention, a 55 pound (0.0605
inch wall thickness) can be used without corrugations for the outer
container without sacrificing buckle and collapsing strength.
With the above arrangement, a hot filled liquid or a vacuum packed
product can be packaged using existing equipment without any
modification thereof.
A further modified form of the invention is illustrated in FIGS. 7
and 8 and the general concept incorporated into this embodiment
could likewise be incorporated into any of the embodiments
previously described. In this embodiment of the invention, the
outer container 130 has a substantially rectangular side wall 132
and has a flat bottom wall that is integral therewith. Preferably,
the outer container 130 is thermoformed from a plastic material
that has heat sealing capabilities. The upper peripheral edge of
outer container 130 preferably has an outwardly directed flange 134
(FIG. 8) and a lip 136 that defines a locking recess 138, as will
be described later.
In this embodiment of the invention, the composite container also
includes an intermediate container or shell 140 that conforms
generally to the configuration of the outer container or shell 130
and also has an upwardly directed flange 142 at the upper
peripheral edge thereof. A third or inner thermoformed plastic
container 144 again conforms to container shells 130 and 140 and
has an outwardly directed flange 146. A suitable plastic film 150,
preferably having heat sealing characteristics is adapted to be
heat sealed to the exposed peripheral surface of the flange 146 of
the inner container 144. Preferably, an overcap or cover 152 has a
pair of flanges 154 at opposite edges thereof which cooperate with
recesses 136 to releasably retain the cover 152 on the container
after the product has been inserted and the film 150 heat sealed to
the open end thereof. The cover could also be attached along one
edge by an integral flexible hinge to flange 134.
The advantages of utilizing a thermoformed multilayer composite
container as illustrated in FIG. 8 that are separately formed and
then inserted within each other are numerous. For example, the
various separate plastic parts could be formed from different
materials that would not be compatible with each other when formed
as a laminated structure. By way of example, the outer container
shell 130 could be formed from a foamed type plastic material that
has little or no permeation resistance while the intermediate liner
or container shell 140 could be formed from a highly permeation
resistant plastic material that would be an excellent oxygen
barrier while the inner container shell 144 could be formed from a
polypropylene that is highly stable and will not contaminate the
product ultimately inserted therein.
The venting of this type of design can be accomplished in several
ways. The first would be to utilize the poor permeation resistance
of the outer container and would permit expansion and contraction
of the inner liners as the positive and negative pressures are
developed in the filling and storage of the containers. If a
nonpermeable outer container is used then the predescribed methods
of providing a vent hole (not shown) in the outer container and
subsequent sealing may be utilized. Still another variation would
be to vent through an air passageway channel 151 located between
outer container flange 134 and intermediate container flange 146.
The air space 153 between outer container 134 and intermediate
container 140 is thus vented to the atmosphere through channel 151
and past film 150 before sealing of film 150 to upper peripheral
surface 155 on outer container 130. Film 150 may be sealed to the
top inner container flange 146 after filling but its peripheral
area is not to be sealed to outer container surface 155 until after
necessary venting is accomplished.
Actual tests have shown that the containers constructed in
accordance with the present invention are capable of withstanding
increased buckle pressures, such as for example, when the filled
container is dropped because it is believed that the liner expands
inside the container and the product produces a positive pressure
on the side wall of the outer container to strengthen the side
wall.
Further testing with 2 milligram polypropylene bags assembled into
containers have demonstrated functionality of the invention.
Containers as illustrated in FIG. 6 were produced and packed with
green beans prior to retorting for 20 minutes at 250.degree. F. in
a pressurized retort. After cooling, the samples were examined.
Control cans had nine inches of vacuum as did variables with no
vent holes. Samples with vent holes had significantly reduced
vacuum and all cans were examined for leakage or rupture of the
liner with none detected illustrating support of the liner by the
outer container in the positive pressure mode and the ability of
the liner to contract in the negative pressure mode. Additional
tests were made with thin wall nonvacuum design cans that had
inserted into them thermoformed polypropylene liners with wall
thicknesses ranging from 1 to 6 milligrams prior to hot filling at
190.degree. F. with a noncarbonated juice drink. Samples with no
liners failed due to the negative pressure in what is termed
paneling or distortion of the outer container side wall. None of
these with liners failed. It was further determined that in abuse
testing that if the liner was not capable of equalling or exceeding
the space within the outer container in drop testing that the
hydraulic forces may cause rupture of thin wall liners. Forty-six
ounce juice cans were dropped from heights up to 24 feet with
leakage being induced in control, or those without liners, while
after providing the slightly oversized liner leakage was greatly
reduced.
The unique composite container construction reduces the structural
and geometric requirements so that materials such as paper, foil,
plastics, steel, aluminum, or glass can be used for the outer
container.
It should be pointed out that all embodiments, the term film is
intended to encompass a single sheet or a composite structure such
as a laminated sheet.
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